1. Field of the Invention
This invention relates to an electric apparatus filled with an insulating medium of e.g. an insulating oil, an insulating gas, etc. such as a transformer, a reactor, etc.
2. Description of the Related Art
Among electric apparatuses filled with the insulating medium of the insulating oil, a sectional view of an core-form transformer is shown in FIG. 5. A developed view of the portion of an insulating cylinder is shown in FIG. 6. In these figures, reference numeral 1 denotes an iron core with silicon steel laminated; 2 an insulating cylinder arranged on the outer periphery of the iron core 1, which forms a passage A of the insulating medium between itself and a winding; 3 a low voltage winding arranged on the outer periphery of the insulating cylinder 2; and 4a, 4b, 4c intermediate cylinders which are arranged in a shape of multiple cylindrical layers on the outer periphery of the low voltage winding 3 to form insulating barriers. Between the layers, spacers 5a and 5b are separately arranged to form insulating medium passages C and D. Between the low voltage winding 3 and the inner periphery of the insulating cylinder 4a, an insulating medium passage B is formed. Reference numeral 6 denotes a high voltage winding arranged on the outer periphery of the insulating cylinders 4a, 4b and 4c, which forms a passage E for the insulating medium between its inner periphery and the outer periphery of the insulating cylinder 4c. Reference numeral 7 denotes an insulating cylinder arranged on the outer periphery of the high voltage winding, which forms an insulating medium passage F between itself and the outer periphery of the high voltage winding 6.
With respect to the low voltage winding 3 and the high voltage winding 6, between the insulating medium passage A or E on the side of the inner periphery and the insulating medium passage B or F on the side of the outer periphery, partitions are arranged for every several disks. In such a configuration, the low voltage winding 3 and the high voltage winding 6 are constructed so that during the running of the apparatus, the insulating medium flows a zigzag form in a direction of an indicated arrow. The insulating medium passages C and D formed between the adjacent ones of the insulating cylinders 4a, 4b and 4c are adapted to communicate upward.
In the transformer constructed described above, the portions of the low voltage winding 3 and the high voltage winding 6 are effectively cooled by the zigzag flow of insulating medium which flows laterally between the respective adjacent disk coils. Since the potential difference between the disk coils of the low voltage winding 3 and high voltage winding 6 is small, the phenomenon of flow charging occurs to a low degree even at a high flow rate. On the other hand, the insulating medium paths C and D formed by the layers of the insulating cylinders 4a, 4b and 4c, which are located between the low voltage winding 3 and high voltage winding 6, are under a high electric field strength. Therefore, when the insulating medium flow through the insulating paths C and D, the surface of each of the insulating cylinders 4a, 4b and 4c is charged with a negative polarity, whereas the insulating medium is charged with a positive polarity. Thus, charges are accumulated on the surface of each of the insulating cylinders 4a, 4b and 4c. This may give rise to partial discharging on the surface, which is a cause of reducing the reliability of insulation.
As described above, the conventional structure having the insulating medium paths C and D between the insulating cylinders 4a, 4b and 4c which form insulating barriers between the low voltage winding 3 and high voltage winding 6 has the following disadvantage. When the insulating medium flows through the insulating medium paths C and C which are under a high electric field strength between the low voltage winding 3 and high voltage winding 6, the phenomenon of flow charging occurs, thereby reducing the reliability of insulation.
This invention has been accomplished in order to solve the above problem, and intends to provide an electric apparatus which can prevent occurrence of a phenomenon of flow charging in a structure in which insulating medium paths are formed between insulating cylinders which form insulating barriers between an iron core and a low voltage winding, between the low voltage winding and a high voltage winding or on the periphery of the high voltage winding.
To achieve the above object, according to a first aspect of the invention, there is provided an electric apparatus defined in which insulating cylinders having different diameters are arranged in a shape of multiple cylinders between the iron core and the low voltage winding, between the low voltage winding and the high voltage winding and on the periphery of the high voltage winding; spacers are separately arranged between layers of the plurality of insulating cylinders to form a plurality of insulating medium paths; and a flow stopping member for stopping the flow of the insulating medium in the insulating medium paths which is made of an insulating material with a low density is arranged at at least one of the upper and lower ends of each of the insulating medium paths.
According to a second aspect of the invention, in the electric apparatus defined in the first aspect, said flow stopping member is made of a material in the form of a mat of insulating fiber.
According to a third aspect of the invention, in the electric apparatus defined in the third aspect, said flow stopping member configured as described in claim 2 has a volume ratio of insulating fiber of 5-50%.
According to a fourth aspect of the invention, in the electric apparatus, at least one of the upper and lower ends of said insulating medium path is covered with a sheet of said flow stopping member, configured as described in the first aspect, having a volume ratio of insulating fiber of 5-50%.
According to a fifth aspect of the invention, in the electric apparatus, a low voltage winding and a high voltage winding are superposed to arrange a winding in a vertical direction, iron cores are stacked at a center and periphery of the winding, a plurality of layers of insulating barriers are arranged on the outer periphery of the stacked iron cores at the center of the winding and spacers are separately arranged between layers of the plurality of insulating barrier to form a plurality of insulating medium paths in a vertical direction, and a flow stopping member for stopping the flow of the insulating medium in the insulating medium paths which is made of an insulating material with a low density is arranged at at least one of the upper and lower ends of each of the insulating medium paths.
According to a sixth aspect of the invention, in the electric apparatus, a low voltage winding and a high voltage winding are superposed to arrange a winding in a vertical direction, iron cores are stacked at a center and periphery of the winding, a plurality of layers of insulating barriers on the outer periphery of the stacked iron cores at the center of the winding and spacers are separately arranged between layers of the plurality of insulating barrier to form a plurality of insulating medium paths, a flow stopping member for stopping the flow of the insulating medium in the insulating medium paths which is made of an insulating material with a low density is arranged at at least one of the upper and lower ends of each of the insulating medium paths, and a flow suppressing member is arranged in the insulating barriers and each of the iron cores, said flow suppressing member having a length providing a suitable flow rate of the insulating medium.